Ferrous alloy



Patented June 5, 1934 UNITED STA FERROUS ALLOY I Frank R. Palmer,Reading, Pa., assignor to Th Carpenter SteelCompany, Reading, Pa.,acorporation of New Jersey No Drawing. Application January 28, 1932,

Serial No.

Claims.

This invention applies to austenitic ferrous alloys which are difficultto machine, and has for its object improving the machinability of suchalloys by the addition of suitable elements as 5 hereinafter described.

Corrosion resisting ferrous alloys are known to the art containingessentially from 4% to 60% chromium; the chromium content beingessential in all cases to secure corrosion resisting properties. Asubdivision of these ferrous alloys containing the essential chromiumelement is austenitic in character, usually by reason of the furtheraddition of a metal like nickel or manganese, illustrated by suchcombinations as:

Chromium Nickel Manganese Percent Percent Percent 18 8 Less than 1. 3 20Less than 1. 20 12 12 Less than 1. 15 Less than 1. 85 15 Less than 1. 18Less than 1 8 Chromium, manganese and nickel can be com- 25 bined inmany ways to produce predominantly austenitic alloys, but usually thetotal content of these metallic alloying elements will fall between 10%and 50%, the principal part of the balance I have discovered thatphosphorus or arsenic, or such elements as are known to embrittle aferrous alloy, can be advantageously employed in connection with thehigh. sulphur described of austenitic alloys beyond the point that isfeasible with the use of sulphur alone. I find that the use of anembrittling agent like phosphorus or arsenic, without the high sulphuraddition, is comparatively ineffective in realizing the purpose of myinvention, which contemplates that phosphorus should always beaccompanied by an appropriate content of high sulphur.

In experimenting with the use of phosphorus as an embrittling agent inconjunction with high sulphur, I find that .05% gives slight butnoticeable improvement; that excellent results can be secured withphosphorus between .08% and .15% while a frequently unnecessary degreeof brittleness can be' introduced with a phosphorus content as high as.50%. I would recommend that a phosphorus content of .20% to 50% be usedonly where the physical toughness of the resulting alloy is of minorconsequence in the purpose for which it is to be used.

My invention is well illustrated by comparing the machinability of fourferrous alloys having -the following essential compositions:

being iron.

Carbon plays no essential part in the effective use of my invention butit is well-known to the art that the percentage of carbon present in aferrous alloy greatly affects its austenitic nab) ture; it beingunderstood that higher carbon alloys yield stable austenite with lowerpercentages of metallic alloying elements, but frequently with increasedmachining difllculty. For the purpose of this invention, a ferrous alloyis considered austenitic when it contains substantial quantities ofaustenite in the structure, after slow cooling from above its criticaltransformation points.

My Patent No. 1,835,960 issued December 8, 1931, explains fully how themetalloid sulphur, when added to any corrosion resisting alloy steelcontaining as an essential element chromium between 7% and 30%, reducesthe high-friction character of the alloy and so makes it easier tomachine; while other experiments show that the same effects obtain withchromium up to 60%. This use of sulphur is effective in the caseofaustenitic, high chromium, corrosion resisting alloys, but, owing tothe great toughness of these austenitic alloys, I have found itdesirable that 55 the machinability be still further improved.

Chromium Nickel Sulphur Phosphorus Percent Percent Percent Alloys (a)and (d) are both'quite difflcult to machine, whereas alloy (0) isnoticeably better, and alloy (b) is by far the best; In comparing alloys(a) and (b) for example, machining hexagon nut blanks in an automaticscrew machine from hexagon bars, production on alloy (at) was 3 nuts perminute while on alloy (b), production was 6 nuts per minute; In sawinghexagon bars of alloys (a) and (b) in a power hack saw, the timerequired to make a single cut was 80 seconds and 30 secondsrespectively.

My invention applies, not only to austenitic corrosion resisting alloysbut also to austenitic ferrous alloys in general, such as thebi-metallic austenitic alloys of iron and manganese, iron and nickel,and any other combination of metallic alloying elements which willproduce with iron an austenitic alloy, as manganese and nickel jointlyor manganese nickel and chromium.

in my said patent to increase the machinability v 0 The embrittlingmetalloid phosphorus is usually added to the molten bath in the form offerrophosphorus, an alloy of iron and phosphorus containing about 20%phosphorus, by manipulation well understood by those familiar with theart.

In the subjoined claims the term balance substantially iron contemplatesthat the balance of the composition is largely iron but may containpercentages of non-ferrous alloying elements of such nature and in suchquantity as to not alter the basic nature of the alloy for purposes ofmy invention. For example, in my austenitic" group there occurs a steelhaving the following nominal composition:

C .10% Cr 18.00% Ni 8.00%

Many modifications of this basic composition are well known to the artcontaining added percentages of other alloying elements as:

C .10% Cr 18.00% Ni 8.00% Ti 1/2.0%

O .103; Cr 18.00% Ni 8.00% Cu 2.45% C .10 0 Cr 18.00% Ni 8.00% W 3.80% O.10% Cr 18.00% Ni 8.00% IMO 3.42% C .10% Cr 18.00% Ni 8.00% Si 4.59% C.10% Cr 18.00% Ni 8.00% Al 2.00%

tween 5% and 46% with a total percentage of said elements between 10%and 50%, sulphur between .16% and 1.80%, phosphorus between .06% and.50%, the balance being substantially iron and the resulting alloy beingdistinguished by relatively free machining quality.

2. An austenitic ferrous alloy containing essentially chromium between10% and 25%, nickel between 5% and 15%, sulphur between .16% and 50%,phosphorus between 06% and 25%, the balance being substantially iron andthe resulting alloy being characterized by relatively free machiningproperties.

3. An austenitic alloy containing approximately 18% of chromium, 9% ofnickel, 30% of sulphur, .15% of phosphorus the balance beingsubstantially iron and the resulting alloy being characterized byrelatively free machining properties.

4. A corrosion resisting austenitic alloy containing chromium between 4%and 45% and alloy of the group manganese nickel between 5% and 46% witha total percentage of said elements between 10% and 50%, sulphur between.16% and 1.80%, and an embrittling agent of the 100 groupphosphorus-arsenic between .06% and 50%, the balance being substantiallyiron and the resulting alloy being characterized by relatively freemachining properties.

5. An austenitic alloy containing between 5% 135 and 50% of metallicalloy of the group manganese-nickel-chromium, between .16% and 1.80% ofsulphur, and between 06% and .50% of embrittling agent of the groupphosphorus-arsenic, the balance being substantially iron and the re- 11sulting alloy being characterized by relatively free machiningproperties.

FRANK R. PALMER.

